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U.  S.  DEPARTMENT  OF  AGRICUL  I  i  RE, 

BUREAU  OF  PLANT  [NDU8TRY-    BOLLBTLfl  NO,  871 


ts 


SOUK  EFFECTS  OF  REFRIGER; 
ON  SULPHURED  AM)  I  X S U L- 
PHURED  IIUI'S. 


BT 


W    W.  STOGKBERQEB,  Physiologist, 

AND 

FI1ANK    UAKAK,    Chemical    BiolOffitt, 
Drug  Plant,    PoitOnOUt-Plant,    Phytiologioal,   and    Fermentation    Investigations. 


WASHINGTON: 

GOVERNMENT    PRINTING  OFFICE. 

1912. 


U.  S.  DEPARTMENT   OF  AGRIC1   Ml  RE. 

BUREAU  OF  PLANT  INDUSTRY     BULLETIN  NO.  871 

it     1.  ■.  \I . l.t  i\\  V,     |  RM, 


SOME  EFFECTS  OF  REFRIGERATION 

ON  SULPHURED  AND  UNSUL- 

PHURED  HOPS. 


BT 

TV.  W.  STOCKBEBGER,  PhyaMagU*, 

AND 

FRANK    ItAUAK.    Chemical    BiolOffitt, 
Drug-Plant,    Poisonous-Plant,    Physiological,    and    Fermentation    Investigation*. 


"SsssSXnSra^ 


w  vstrrvi,  TOW: 

GOVFRNMF.NT    PRINTING    OFFICE. 
1912. 


BUREAU  OF  PLANT  INDUSTRY. 


Chief  of  Bureau,  Beverly  T.  Galloway. 
Assistant  chief  of  Bureau,  William  a.  Taylor. 
Editor,  J.  E.  Rockwell. 
Chief  Clerk,  James   E.  Jones. 


Drug-Plant,    Poisonous-Plant,    Physiological,    and    Fermentation    Investigations. 

scientific  staff. 

Rodney  H.  True.  Physiologist  in  Charge. 
A.  B.  Clawson,  Heinrich  Hasselbring.   C.  Dwight  Marsh,   \V.   W.   Stockberger,  and   Walter 

Van  Fleet,  Physiologists. 
Carl  L.  Alsberg,  H.  H.  Bartlett,  Otis  F.   Black,  H.   H..  Bunzel,   Frank  Rabak,  and  A.   F. 

Sievers,   Chemical  Biologists. 
W.  W.  Eggleston,  Assistant  Botanist. 

S.  C.  Hood,  G.  F.  Mitchell,  James  Thompson,  and  T.  B.  Young,  Scientific  Assistants. 
Hadleigh  Marsh,  Assistant. 
G.  A.  Russell,  Special  Agent. 
271 


ADDITIONAL  COPIES  of  this  publication 
XL  may  be  procured  from  the  Supebintenb- 
ENt  of  Documents,  Government  Printing 
Office,  Washington,  D.  C,  at  .1  cents  per  copy 


LETTER  OF  TRANSMITTAL 


U.  S.    I  >i  l'\ici  mini    OF    A.GHK  i  1  i  1  KB, 

l'.i  i;i   \i    in    Pl.w  I    [NDU8TBT, 

Ollli    I       m|        I   HI       (ll  III'. 

Washington,  />.  <..  September,   18,  1912. 

Sn::  I  have  tin-  honor  to  transmit  herewith  and  to  recommend 
for  publication  a<  Bulletin  NO.  -71  of  the  series  oi  this  Bureau  a 
manuscript  by  Dr.  W.  W.  Stockberger,  Physiologist,  and  Mr.  Prank 
Rabak,  Chemical  Biologist,  entitled  "Some  Effects  of  Refrigeration 
on  Sulphured  and  Dusulphured  Hop-."  submitted  by  Dr.  R.  II.  True, 

Physiologist  in  Charge  of  the  Office  of  Drug-Plant,  Poisi is-Plant, 

Physiological,  and  Fermentation  Investigations. 

In  this  paper  is  discussed  some  of  the  changes  which  occur  in  im- 
portant constituents  of  hops  under  different  conditions  of  storage  and 
i  comparison  is  made  of  the  relative  efficacy  of  certain  methods  for 
pn>\  enting  undesirable  changes  in  hop  constituents. 

This  bulletin  shows  thai  both  refrigeration  and  sulphuring  retard 
changes  in  the  volatile  constituents  oi  imp-  and  that  the  determina- 
tion of  the  value  of  hops  From  the  aroma  varies  according  to  indi- 
vidual preference  for  or  dislike  of  one  or  the  other  of  the  aromatic 
constituents.  The  conclusions  drawn  from  a  comparison  of  valua- 
tions made  from  both  physical  and  chemical  standpoints  will  be  of 
practical  importance  to  all  interested  in  the  hop  industry. 
Respect  fully. 

13.    T.    (  i  W.l.uWAY. 

CkU  ]  of  Bureau. 
Hon.  .1  \mi>  Wilson, 

St  cretary  of  Agru  idture. 

271 

3 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/effhopoOOunit 


C  0  X  T  E  N  T  S 


Paee. 

Introduction 7 

Preparation  of  the  hops  studied 8 

Physical  changes  in  the  hope  in  cold  and  in  ordinary  storage 8 

Changes  in  the  volatile  constituents  of  hops  in  cold  and  in  ordinar)  storage 11 

Changes  ID  the  hop  resins 1  > 

Physical  and  chemical  valuation  compared 16 

i  .en. t.iI  significance  of  the  results 19 

Summary 20 

L'Tl 

5 


u  p  i     788 


SOME  EFFECTS  OF  REFRIGERATION  ON 

SULPHURED  AND  UNSULPHURED  HUPS. 


INTRODUCTION. 

Opinions  arc  greatly  divided  as  to  the  desirability  or  general  ex- 
pediency  of  the  practice  of  treating  hops  with  the  funic-  <»f  burning 
sulphur  during  the  process  of  drying.  This  process,  which  in  the 
United  States  is  termed  "sulphuring,"  has  been  Long  in  vogue  and 
has  come  to  be  regarded  as  an  essential  pari  of  the  method  of  prepar- 
ing hops  for  market.  The  use  of  sulphur  as  an  adjunct  to  hop 
drying  apparently  originated  in  England  and  from  the  first  was 
regarded  as  a  more  or  Less  effective  mean-  of  checking  the  tendency 
of  newlj  packed  hops  to  heat  and  -pod  in  the  bale.  Later,  other 
virtue-  were  claimed  for  sulphuring  in  addition  to  thai  of  pre- 
servative action,  and  tho-e  who  advocate  the  use  of  sulphur  uow 
believe  that  it  favorably  affects  the  hops  by  changing  and  improv- 
ing the  color,  by  hastening  the  drying  through  causing  the  rapid 
deatli  of  the  cells,  and  by  preventing  fermentation,  thereby  improv- 
ing the  keeping  qualities. 

Aside  from  sulphuring,  a  number  of  other  expedients  have  been 
resorted  to  for  the  purpose  of  delaying  or  retarding  the  changes 
which  normally  occur  in  the  chemical  constituents  of  hops  after 
they  have  been  dried  and  baled.  Of  these  expedient-  refrigeration 
is  the  most  widely  used  and  from  many  considerations  it  i-  perhaps 
the  most  efficient  and  generally  satisfactory  method  of  preservation 
that  has  as  yet  been  employed. 

The  sulphuring  of  hop-  is  such  a  common  practice  in  the  United 
State-  that  practically  all  hops  placed  in  cold  storage  may  he  re- 
garded  as  having  absorbed  a  varying  quantity  of  sulphurous  acid, 
depending  to  a  certain  extent  upon  the  quantity  of  sulphur  used 
at  the  time  of  drying.  Since  both  sulphuring  and  cold  storage  are 
held  to  he  efficient  agents  in  retarding  changes  in  the  essential  con- 
stituent.- of  hops,  the  diminished  rate  of  deterioration  of  sulphured 
hop-  in  cold  storage  must  he  due  to  the  combined  action  of  these 
two  processes.    Bowever,  the  relative  efficacy  of  these  two  proa 

271  7 


8  SOME   EFFECTS   OF   REFRIGERATION   ON   HOPS. 

or  the  extent  to  which  the  one  or  the  other  alone  would  accomplish 
the  desired  result,  is  usually  a  subject  of  approximate  estimation 
only. 

For  the  purpose  of  obtaining  some  experimental  data  upon  the  pre- 
servative action  on  hops  of  sulphuring  and  cold  storage,  singly 
and  in  combination,  suitable  material  was  prepared  and  held  under 
observation  for  several  years.  The  results  of  this  study,  which  are 
given  in  some  detail  in  this  bulletin,  indicate  that  both  cold  storage 
and  sulphuring  tend  to  delay  certain  undesirable  chemical  changes 
and  that  the  usual  trade  judgment  can  not  always  be  relied  upon  to 
give  an  accurate  measure  of  the  extent  to  which  these  changes  have 
occurred.  However,  it  is  fully  realized  by  the  writers  that  further 
experimentation  is  necessary  before  the  conclusions  drawn  from  this 
work  can  be  considered  to  have  a  general  application. 

PREPARATION   OF    THE   HOPS   STUDIED. 

The  hops  which  furnished  the  materials  for  the  observations  here 
recorded  were  all  picked  from  the  same  part  of  a  field  on  a  hop  ranch 
in  the  Sacramento  Valley  on  August  30,  1907,  and  were  dried  on  the 
same  day  under  the  senior  writer's  supervision.  As  the  hops  were  re- 
ceived from  the  field  they  were  equally  distributed  to  two  duplicate 
stove  kilns  until  each  had  received  a  load  of  about  4,500  pounds,  green 
weight.  The  fires  were  lighted  and  the  temperature  of  each  kiln 
was  gradually  raised  to  a  point  between  130°  and  140°  F.,  between 
which  limits  it  was  maintained  until  the  drying  was  completed.  On 
one  of  these  kilns  110  pounds  of  sulphur  was  burned  under  the  hops 
during  the  drying,  which  required  13  hours;  on  the  other  kiln  no 
sulphur  was  used  and  the  time  required  for  drying  was  18  hours. 
The  dry  hops  from  each  of  these  two  kilns  were  separately  deposited 
in  the  cooling  room  and  on  September  2  two  bales  of  the  usual  com- 
mercial type  were  prepared  from  the  unsulphured  hops  and  two  from 
those  which  had  been  heavily  sulphured.  These  four  bales  were  con- 
veyed to  Sacramento,  where  two  bales,  one  of  sulphured  and  one  of 
unsulphured  hops,  were  placed  in  cold  storage  at  36°  F.  in  the  hop 
storeroom  of  the  Buffalo  Brewing  Co.,  and  the  two  remaining  bales, 
one  of  which  was  sulphured  and  one  unsulphured,  were  placed  in 
ordinary  storage  in  the  Clunie  warehouse, 

PHYSICAL   CHANGES   IN   THE  HOPS   IN   COLD   AND   IN   ORDINARY 

STORAGE. 

As  a  rule,  it  is  difficult  to  correlate  the  valuation  of  hops  as  de- 
termined from  their  physical  characters  with  the  indications  of  their 
value  derived  from  chemical  analysis.     In  the  present  case,  however, 

271 


rill  BIOAJ    <ii  \N'i  -    in    HOPt    IN  BTOBAGB.  9 

some  chemical  determinations  were  made  which  are  not  ordinarily 
taken  into  account  in  analyzing  hops,  and  the  results   fun 
interesting  parallels  when  compared  with  the  relative  rank  in  quality 
of  the  four  bales  of  hops  as  fixed  l>\  physical  valuation. 

In  order  t"  have  the  differences  in  physical  condition  expressed  in 
the  language  of  the  trade  and  as  nearlj  as  possible  from  the  trade 
viewpoint,  samples  were  drawn  from  time  t«>  time  from  the  four  bales 
and  submitted  to  various  trade  experts,  who  were  asked  i"  report 
their  impressions  as  to  the  general  condition  and  relative  meril  of 
the  various  samples. 

Early  in  April,  1908,  after  the  hops  had  been  in  storage  for  -even 
months,  samples  were  drawn  from  each  of  the  four  bales  and  sub- 
mitted i"  five  trade  experts,  all  of  whom  concurred  in  the  following 
report  made  by  one  of  t!mir  number: 

We  have  examined  these  samples  ai   to  tbeli  condition  a1  the  present  time 
If  there  was  any  difference  between  cold  and  regularly  Btored  hops,  and 
we  are  of  the  Bame  opinion  thai  there  is  no  difference  between  1 1 * « -  cold  Btored 
and  regularly  stored  bops. 

The  bales  were  not  dimpled  a  second  time  until  midsummer,  ami 
during  the  time  which  had  elapsed  since  the  firsl  sampling  the  hops 
in  ordinary  storage  had  been  subject  to  the  influence  of  tin-  hot  and 
dry  weather  which  prevails  in  the  Sacramento  Vallej  ai  this  3ea  on 

of  (lie  year.  Naturally,  it  was  expected  that  at  this  time  certain  dif- 
ferences would  he  apparent  in  the  hops  under  different  condition,  of 
Storage.      On   July   24,    L908,   -ample-    were   drawn    and   submitted   to 

an  expert  hop  buyer,  who  reported  on  them  a-  follows: 

I'n muI ph u red  cold-stored  hops,  fine  fresh  hop  flavor;  good  oilj  feeling; 
aroma  almost  as  good  as  new  hops  and  seems  m  !»■  about  the  same  a-  tbnt  of 
the  sulphured  cold  stored  hops. 

Sulphured  cold-stored  hops.     Fine  fresh  hop  flavor;  g l  oily  feeling;  aroma 

almost   as  •_" 1  as  new   hops,  but   COlOI  somewhat    lighter   than   the  Color  <'f   the 

onsnlpbured  sample  above  described. 

Unsulphured  ordinary-stored  hops.  Flavor  decidedly  that  of  old  hops  ascom- 
pared  with  the  c.>id  stored  samples;  feeling  dry:  lupulin  not  very  sticky:  color 
about  the  same  as  the  color  of  the  unsulphured  -ample  above. 

Sulphured  ordinary-stored  hops.  Fine  fresh  flavor;  good  oily  feeling;  aroma 
almost  as  good  as  new  hops,  but  the  color  somewhat  lighter  than  the  color  of 
the  unsulphured  sample  above  described. 

At    this  time  it    is  decidedly  noticeable  that    the  cold  Stored   hops  have  by  far 
the  besl   flavor  and  that   they  feel  almost  as  oily  as  new  hops,  while  the  ordinary 
Stored  hops  are  becoming  poorer. 

This  Judgment    was   taken   within  an   hour  after   the   hales   had   hem   Sampled, 

ami  on  coming  Into  the  room  where  the  samples  had  been  placed  I  thought  that 

the  excellent  aroma  was  dif  i"  new  hops.      I  was  really  surprised  at   the  -roar 
difference  in  the  aroma   between   the  ordinary  timed  and  cold-stored   bops,   but 
g:.i.:;  -  12 2 


3    S    M    35 


10  SOME    EFFECTS   OF    REFRIGERATION    ON    HOPS. 

mi  comparing  color  I  can  Dot  notice  any  serious  difference  between  sulphured 
and  unsulpbured  bops  in  either  case. 

These  same  samples  were  next  submitted  to  a  second  expert,  who 
made  the  following  statement : 

The  difference  between  the  ordinary-stored  ami  the  cold-stored  hops  is  now 
very  noticeable.  The  unsulpbured  cold-stored  sample  has  a  very  good  flavor  and 
looks  fresh  and  bright.  The  unsulpbured  ordinary-stored  sample  has  not  such 
;i  good  flavor  as  the  former,  is  very  much  drier,  and  is  becoming  rapidly  aged. 
The  difference  between  these  two  is  particularly  noticeable  in  the  appearance 
of  the  sides  of  the  samples,  the  side  of  the  cold-stored  sample  showing  up  much 
brighter  and  fresher  than  that  of  the  other. 

The  sulphured  cold-stored  sample  has  a  fine  fresh  flavor  and  is  a  particu- 
larly well  kept  hop.  while  the  sulphured  ordinary-stored  sample  lias  a  musty. 
old  flavor  and  is  rather  dried  out.  The  difference  between  these  two  samples 
is  not  so  much  in  the  appearance  as  in  the  aroma. 

On  the  day  following,  these  samples  were  submitted  to  a  brew- 
master,  who  delivered  the  following  opinion  : 

The  cold-stored  hops  have  a  lighter  color  as  compared  with  the  ordinary- 
stored  hops,  the  lupulin  is  bright  and  shiny,  the  hops  have  a  very  oily  and 
sticky  feeling,  and  the  aroma  is  almost  like  that  of  new  hops. 

The  ordinary-stored  hops  have  a  dull,  dry  color;  the  lupulin  is  not  so  bright 
and  appears  to  be  hard  and  dry,  with  very  little  oil  as  compared  with  the  cold- 
stored  hops;  the  flavor  is  decidedly  different  and  very  much  like  that  of  old 
hops. 

The  hales  were  not  sampled  again  until  February  13.  1009,  eighteen 
months  after  they  were  first  placed  in  storage.  The  samples  drawn 
on  this  date  were  first  submitted  to  the  brewmaster  previously  men- 
tioned, and  his  judgment  as  to  their  relative  merit  was  stated  thus: 

The  sulphured  and  unsulphured  cold-stored  samples  are  respectively  superior 
in  flavor  to  the  corresponding  ordinary-stored  samples.  The  sulphured  samples 
in  cold  and  ordinary  storage  are  far  superior  both  in  flavor  and  color  to  the 
unsulphured  samples. 

The  samples  were  next  submitted  to  a  trade  expert,  who  gave  the 
following  opinion : 

There  is  a  very  great  difference  between  the  cold-stored  and  ordinary-stored 
hops.  The  cold-stored  samples  are  much  brighter  in  appearance,  have  much 
more  flavor,  contain  much  more  moisture,  and  their  lupulin  is  much  brighter 
than  the  ordinary-stored  samples.  The  cold-stored  samples  would  pass  for  new 
hops,  while  the  ordinary-stored  samples  show  their  age  and  could  not  pass  for 
anything  else  than  "  olds."     By  new  hops  I  mean  the  1CK)S  crop. 

Of  the  cold-stored  hops  the  unsulphured  sample  seems  to  have  a  trifle  more 
flavor  than  the  sulphured  one,  but  the  latter  has  a  sweeter  flavor,  which  I 
believe  would  be  preferred.  The  lupulin  in  both  these  samples  is  very  fresh 
and  moist,  but  that  in  the  sulphured  sample  is  a  trifle  the  brighter.  The  sul- 
phured sample,  though  in  appearance  fresher  than  the  unsulphured  sample,  is 
not  as  moist  as  the  latter. 

Of  the  ordinary-stored  hops  the  unsulpbured  sample  has  much  more  flavor 
than  the  sulphured  sample,  the  latter  having  very  little  flavor  at  all.  The 
271 


OHANGEfl  I  \    \t'i   \  i  11  I    CON8TIT1   1  WTS  01     BOPti  i\    3TOKAOB.        11 

i iipni in   in   iii<-  sulphured  sample  la  n  trifle  brighter  In  the  other. 

The  uneulphnred  sample  li  much  more  motat  than  the  Rulphured  anmple  thougli 
the  latter,  before  o  detailed  examination,  appears  to  i"  the  freeher  "i  the  two, 
m  c lltton  that  can  be  traced  to  the  brlghtenli  f  the  aulphur. 

Since  the  Bulphured  cold-stored  hops  natural]}  conformed  mosl 
closely  m  appearance  and  general  i  ondition  to  the  hops  usually  found 
in  the  t  rade  it  was  expected  that  the>  would  be  ranked  first  in  quality, 
nnd  such  proved  t<>  be  the  case  when  the  several  expressions  of  judg 
iiii'iu  l>\  the  trade  experts  were  analyzed.  With  respect  to  the  other 
lots  of  hop-,  however,  opinion  was  divided  and  the  usual  difference* 
in  trade  judgment  of  quality  are  here  well  illustrated.  The  rank  in 
order  of  merit  as  fixed  by  four  of  the  judges  wag  as  follows: 

Sulphured  cold-stored  hops                         i  i  l.  1. 

Unsulphnred  cold-stored  bopa  2  2  •"..  '_'. 

Sulphured  ordlnarj  Btored  bops      ::  i  -.  l. 

rjnsnlphured  ordlnarj  Btored  bops  4,  3  I, 

CHANGES    IN    THE    VOLATILE    CONSTITUENTS    OF    HOPS    IN    COLD 
AND   IN   ORDINARY   STORAGE. 

On  September  1<>.  1909,  portions  <>f  the  four  bales  of  hops  under 
consideration  were  withdrawn  from  storage  and  subjected  to  steam 
distillation  to  remove  the  volatile  oils,  which  were  then  dried  and 
purified  and  later  examined  to  determine  their  degree  of  acidity  and 
ester  content.  These  factors,  together  with  the  percentage  of  yield 
of  volatile  oil,  are  given  in  Table  I. 

Tabu    I.     Comparison  of  rolatih  oih  from  nulphured  and  unsulphured  li"/^  in 
cold  and  in  ordinal}    vtoragt   for  two  years. 


mined. 


oil.   nuiiilxT.    number. 


Rulpnured  roUtatoreri   hops  

Unsulphured  raid-stored  hops 9.0 

Sulphured  ordinary-stored   hops •  lj."> 

Unsulpbured  ordln  hope 


103 
16] 


Aii  inspection  of  this  table  reveals  the  following  interesting  facts: 

i  1 1  The  yield  of  oil  is  twice  as  great  in  the  cold-stored  hops  as  in 
those  in  ordinary  storage. 

(2)  The  acidity  lit'  the  oil  from  the  cold-stored  hop-  is  fai 
than  that  of  the  hops  in  ordinary  storage. 

(3)  The  <>il  from  the  sulphured  hop-  in  ordinary  storage  -how-  an 
increase  of  71.2  per  cent  in  acidity  over  that  from  the  hop-  in  cold 
-!'i  aire,  while  the  oil  from  the  un-ulphured  hop-  in  ordinary  storage 
-how-  an  increase  of  ~:).:)  per  cent  in  acidity  over  that  of  the  oil  from 
those  in  cold  storage. 

271 


12  SOME   EFFECTS   OF   BEFBIGEEATION    OX    HOPS. 

(4)  The  oil  from  the  unsulphured  cold-stored  hops  shows  an  in- 
crease of  23.2  per  cent  in  acidity  over  that  from  the  hops  that  were 
sulphured,  while  the  oil  from  the  unsulphured,  ordinary-stored  hops 
shows  an  increase  of  24.8  per  cent  in  acidity  over  that  from  the  hops 
that  were  sulphured. 

(5)  The  oil  from  the  unsulphured  ordinary-stored  hops  shows  an 
increase  of  113.6  per  cent  in  acidity  over  the  oil  from  sulphured  cold- 
stored  hops. 

(6)  The  ester  content  of  the  oil  from  the  sulphured  hops  is  much 
less  than  that  of  the  oil  from  the  unsulphured  hops. 

(7)  The  oil  from  the  unsulphured  ordinary-stored  hops  shows  an 
increase  of  23  per  cent  in  ester  content  over  that  from  the  hops  in  cold 
storage,  while  the  oil  from  the  unsulphured  hops  in  ordinary  storage 
shows  an  increase  of  46.0  per  cent  in  ester  content  over  the  oil  from 
those  in  cold  storage. 

(8)  The  oil  from  the  unsulphured  cold-stored  hops  shows  an  in- 
crease of  32  per  cent  in  ester  content  over  the  oil  from  the  sulphured 
cold-stored  hops,  while  the  oil  from  the  unsulphured  ordinary-stored 
hops  shows  an  increase  of  57.2  per  cent  in  ester  content  over  that 
from  the  sulphured  hops  in  ordinary  storage. 

(9)  The  oil  from  the  unsulphured  ordinary-stored  hops  shows  an 
increase  of  93.5  per  cent  in  ester  content  over  that  of  the  oil  from  the 
sulphured  cold-stored  hops. 

This  analysis  gives  an  index  of  the  relative  efficacy  of  sulphuring 
and  cold  storage  in  controlling  changes  in  acidity  and  ester  content 
of  the  hop  oils  during  the  first  two  years  of  storage.  The  percentages 
of  increase  in  acidity  as  between  cold  and  ordinary  storage  are 
approximately  three  times  the  corresponding  increase  as  between  the 
sulphuring  and  nonsulphuring.  This  would  apparently  indicate 
that  cold  storage  is  three  times  as  effective  as  sulphuring  in  retarding 
increase  in  acidity.  With  respect  to  ester  content,  the  increase,  as 
between  the  oils  from  cold  and  ordinary  stored  hops,  is  twice  as 
great  in  unsulphured  as  in  sulphured  hops;  also  as  between  sulphured 
and  unsulphured  hops  the  increase  in  the  ester  content  of  the  oil  is 
twice  as  great  in  ordinary  storage  as  in  cold  storage.  This  would 
seem  to  show  that  cold  storage  and  sulphuring  are  about  equally 
effective  in  retarding  the  increase  in  the  ester  content  and  that  the 
two  combined  exert  double  the  effect  of  either  acting  alone. 

On  December  1.  1910,  fifteen  months  later,  a  second  set  of  samples 
was  taken  from  the  four  bales  in  storage  and  the  volatile  oils  removed 
by  distillation.  The  results  of  the  examination  of  these  oils,  which 
are  given  in  Table  II,  show  little  harmony  with  those  of  the  first 
analysis. 

271 


OHANGEB  IN  VOLATILE  CONSTI!  I  HOI'S  IN  STOKAUE.        13 


Taiili    ll      Comparison  o)  volatih  oils  from  tulphured  and  unsulphured  /■ 
cold  and  in  ordinary  it  and  Ihra 


s 


B 

Sii'|.'i 

;.liur.W   urd  I    !»■  -1  •  - 


An  inspection  of  the  table  shows  in  this  case  the  following  rela- 
tions : 

(1)  'l'lic  aciditj  of  the  oil  from  the  cold  stored  hops  is  greater 
than  thai  of  the  <>il  from  the  hop-  in  ordinary  storaj 

(2)  The  acidities  of  the  oils  from  the  In  * i  *~  '"  ordinarj  storage  are 
the  same, 

(3)  The  oils  from  the  unsulphured  col  hops  are  highest  in 
acidity. 

(4)  Tin1  ester  contenl   of  the  oils   from  the  cold-stored  hop 
greater  than  that  of  the  oils  from  the  ordinary  stored  hops. 

(5)  The  oils  from  the  sulphured  hops  in  cold  storage  are  highest 
in  ester  content. 

The  oils  from  the  unsulphured  hops  in  cold  and  in  ordinary 
storage,  respectively,  are  higher  in  ester  content  than  the  <>il  from 
iln>  sulphured  hops  in  ordinary  storage. 

It  is  now  evident  that  the  apparent  effects  of  sulphuring  and  cold 
Btorage  as  shown  by  the  second  analysis  are  almost  the  reverse  of 
those  indicated  by  the  Brst  analysis.  How  these  seeming  discrepan- 
cies may  be  harmonized  can  be  seen  from  an  inspection  of  Table  III. 
in  which  the  results  of  the  two  analyses  are  directly  compared. 

Tm:i  i    [II. — Comparison  of  tin  acidity  and  ester  content  of  the  ',;/,  froti 
phwed  and  unsulphured  hops  wi  cold  and  in  ordinary  storage. 


Sulphured  hops. 

ralphnred  bops. 

Kind  of  <tor 
age. 

Add  num- 

bor. 

Per 

rent- 
age of 

o  am- 
ber. 

1910. 

\.  i.l  num- 
lx>r. 

IVr- 

pont- 
age ..f 

Ester  num- 
ber. 

Per- 

1910 

- 
1910. 

1910 

Ugg 

1910 

■ 
1910. 

1900 

1910 

1910. 

rvi.i 

B0.8      Ml  n 

78 

9.3 

9.0 

53.8 

1M.1 

Ordinary 

U.E 

B2.0 

16.6 

24.0 

IB 

109.0 

Regarding,  first,  the  acidity,  the  data  in  this  table  show  that  the 
percentage  of  increase  in  acidity  was  least  in  the  oils  from  the  hops 
which  yielded  oils  that  were  highest  in  acidity  in  100°  and  greatest 

271 


14  SOME    EFFECTS   OF   BEFBIGBBATIOM    03S    HOPE. 

in  those  lowest  in  acidity  in  1009.     Further,  all  the  percentages  of 

increase  in  acidity  in  1010  are  inversely  proportional  to  the  acidities 
in  L909.  It  is  evident  from  the  first  analysis  that  the  rate  of  change 
in  the  volatile  constituents  under  consideration  was  greatest  in  the 
oils  from  the  unsulphnred  hops  in  ordinary  storage.  These  changes 
would  continue  until  a  maximum  was  reached,  after  which,  owing 
to  the  interaction  between  the  oxidation  products  of  the  various 
organic  constituents  of  the  hops  and  to  the  direct  loss  through  vola- 
tilization, a  decline  in  acidity  would  be  the  normal  result.  Assum- 
ing that  this  maximum  was  reached  between  the  time  of  the  first 
and  the  second  analysis  and  applying  this  explanation  to  the  data 
on  acidity  in  Table  III,  the  oils  from  the  hops  in  ordinary  storage 
may  be  regarded  as  having  passed  the  maximum  and  as  being  in  the 
declining  phase  with  respect  to  acidity.  Since  the  changes  in  the 
unsulphnred  hops  in  ordinary  storage  were  not  artificially  retarded, 
the  oils  from  these  would  naturally  be  nearer  than  the  others  to  the 
maximum  acidity  at  the  time  of  the  first  analysis,  and  hence  the  per- 
centage in  increase  in  1010  would  be  smallest. 

Of  the  hops  in  cold  storage,  the  oils  from  those  that  were  unsul- 
phnred may  be  regarded  as  being  at  or  near  the  maximum  of  acid- 
ity in  1010.  thus  accounting  for  the  high  figure  of  actual  acidity  and 
for  the  relatively  large  percentage  of  increase  in  acidity  during  this 
year.  On  the  other  hand,  the  oils  from  the  sulphured  cold-stored 
hops  had  apparently  not  reached  the  maximum  acidity  in  1010. 
owing  to  the  slower  rate  of  change  in  acidity  in  these  oils  due  to 
the  combined  effect  of  sulphuring  and  cold  storage.  When  viewed 
from  this  standpoint,  the  apparent  discrepancy  between  the  two 
analyses  disappears  and  the  balance  of  evidence  is  in  favor  of  the 
conclusion  (1)  that  under  the  four  conditions  of  this  experiment 
the  acidity  of  the  oil  of  hops  increases  to  a  maximum  and  then  de- 
clines; (2)  that  sulphuring  and  cold  storage  merely  retard  but  do 
not  inhibit  changes  in  acidity;  and  (3)  that  sulphuring  and  cold 
storage  combined  are  more  effective  in  retarding  changes  in  acidity 
than  either  alone. 

With  respect  to  the  esters,  the  data  indicate  that,  in  general,  the 
changes  in  ester  content  have  been  similar  to  the  changes  in  the 
acidity,  although  complicated  by  some  other  factors  which  make 
the  relations  of  these  changes  to  the  conditions  of  storage  less  clear. 
The  first  analysis  show.-  that  the  greatest  changes  in  ester  content 
occurred  in  the  oils  from  the  unsulphnred  hops  and  also  that  the 
oils  from  the  hops  in  ordinary  storage  had  undergone  a  <rreater 
change  than  the  corresponding  oils  from  the  sulphured  and  unsul- 
phured  hops,  respectively,  in  cold  storage.     It  is  possible  that  the 

271 


CHANi  B8  in   \<>i  \Mi  !.  I  0N8TIT1  i  N  I  -  OF   HOPS  IN  STORAGE.       L5 

sulphur  inhibits  the  development  of  estei  beyond  >i  certain  point, 
in  which  case  two  maxima  might  be  expected  one  for  the  oil  from 
sulphured  hops  and  a  higher  one  for  1 1 » *  -  oil  from  unsulphured  hops. 
The  data  of  Table  MI  agree  with  this  assumption,  for  i<  appears  that 
the  «'il-  of  the  unsulphured  ordinary  stored  hopa  were  at  or  near  tli< 
maximum  of  ester  content  in  L909,  which  thereafter  rapidlj  declined, 
as  shown  li\  the  figure  reached  in  1910. 

The  ml  from  the  unsulphured  cold  stored  hops,  which  was  below 
the  probable  maximum  of  ester  content  :ii  the  time  of  analysis  in 
1!M>'.».  shows  an  apparent  increase  of  22.4  per  cent  in  1910;  but,  since 
the  figure  reached  in   1910  is  less  than  the  probable  maximum  as 

indicated  l>\  the  ester  content  of  the  oils  fr the  hops  in  ordinary 

storage  in  L909,  it  seems  evident  that  the  oils  in  the  hops  in  cold 
storage  had  reached  the  maximum  and  entered  upon  the  declining 
phase  before  the  analysis  in  L910.  This  vie*  receives  further  sup 
port  from  the  fact  that  the  oil  from  the  sulphured  cold  stored  hops,  in 
which  tlic  chemical  changes  were  most  retarded,  was  higher  in  ester 
content  in  1910  than  the  oil  from  those  which  were  unsulphured. 

The  oils  of  the  sulphured  hop-  in  ordinary  storage  appear  to  have 
pa>s,-(l  their  maximum  of  ester  content  and  to  be  in  the  declining 

phase  in  L910,  while  those  of  the  Imps  that  were  sulphured  ami  which 

show  the  greatest  increase  in  ester  content  in  1910  appeal-  to  he  at 

or  near  their  maximum.  The  conclusion-  which  are  to  he  drawn 
with  respect  to  the  ester  content,  therefore,  arc  that  sulphuring  re- 
tards the  increase  in  ester  content  and  inhibits  it  beyond  a  certain 
maximum,  that  cold  storage  retards  but  doe-  not  inhibit  increase 
in  ester  content,  and  that  sulphuring  and  cold  storage  combined  are 
more  effective  in  retarding  changes  in  ester  content  than  either  alone. 

CHANGES   IN   THE   HOP   RESINS. 

In  further  pursuance  of  the  plan  of  securing  trade  opinions  with 
respect  to  the  changes  which  had  taken  place  in  the  four  bales  of 
hops  under  different  condition-  of  treatment,  portions  of  these  bales 
were  sent  to  a  firm  which  is  a  large  consumer  of  hops,  with  the  re- 
quest that  the  content  of  soft  and  hard  re-in-  lie  determined  in  each. 
The  first  analysis  was  made  by  the  chemist  of  this  firm  iii  January, 
1910,  two  year-  and  four  month-  after  the  hale-  had  been  first  placed 
in  storage.  One  year  later  a  second  lot  of  -ample-  was  sent  to  the 
same  chemist  anil  by  him  duly  analyzed.  The  results  of  these  two 
analyses  are  given  in  Table  IY\ 

1171 


16 


SOME   EFFECTS   OF   REFRIGERATION    ON   ITOPS. 


Table  IV. — Changes  in   resin  content  in  .sulphured  and  unsulphured  hops  in 

colli  and  in  ordinary  storage. 


Previous  treatment  of  the  hops  analyzed. 


Percentage  of  resins. 


Soft  resins. 


1910 


1911 


Hard  resins. 


1910 


1911 


Total  resins. 


1910 


1911 


Sulphured,  cold  stored 

Unsulphured,  cold  stored 

Sulphured,  ordinary  stored... 
Unsulphured,  ordinary  stored 


10.5 

10.6 
9.8 

9.9 


10.3 
8.7 
7.5 
7.8 


5.5 

5.3 
5.5 
7.0 


5.6 
6.2 


6.4 


16.0 
15.9 

If).  4 
16.9 


15.9 
14.9 
15.0 
14.2 


The  figures  in  the  foregoing  table  give  an  index  to  the  changes 
which  occurred  in  the  resin  content  of  these  hops  during  the  third 
year  of  storage.  The  slightest  change  in  total  resins,  0.1  per  cent, 
took  place  in  the  sulphured  cold-stored  hops,  while  the  greatest 
change,  2.7  per  cent,  is  evident  in  the  unsulphured  hops  in  ordinary 
storage.  The  loss  in  soft  resins  was  least  in  the  sulphured  cold- 
stored  hops,  0.2  per  cent,  and  greatest  in  the  sulphured  ordinary - 
stored  hops,  2.4  per  cent.  The  loss  in  soft  resins  of  the  unsulphured 
hops  was  1.9  per  cent  in  cold  storage  and  2.1  per  cent  in  ordinary 
storage.  As  far  as  the  evidence  from  these  analyses  goes,  it  indi- 
cates  that  sulphuring  diminishes  the  less  of  total  resins,  but  does 
not  diminish  the  loss  of  soft  resins  except  when  followed  by  cold 
storage.  The  greatest  loss  in  soft  resins  was  in  the  sulphured  hops 
in  ordinary  storage,  and.  since  the  soft  resins  alone  are  intrinsically 
valuable,  from  this  standpoint  these  hops  must  be  regarded  as  the 
poorest  of  the  lot.  With  respect  to  these  particular  samples,  the 
balance  of  evidence  indicates  that  there  is  a  distinct  advantage  in 
both  sulphuring  and  cold  storage.  However,  the  margin  of  differ- 
ence in  the  results  of  the  analyses  is  relatively  small,  and  if  the 
soft  resins  were  regarded  as  the  only  measure  of  value,  the  advis- 
ability of  incurring  the  expense  of  long-continued  cold  storage  might 
be  questioned. 

PHYSICAL   AND   CHEMICAL   VALUATION   COMPARED. 

Great  difficulty  is  experienced  not  only  in  harmonizing  the  results 
of  the  physical  and  chemical  estimations  of  the  value  of  hops,  as 
pointed  out  on  a  previous  page,  but  also  in  bringing  into  accord 
the  different  individual  judgments  of  quality,  determined  on  a 
purely  physical  basis.  This  point  has  been  discussed  at  some  length 
in  a  previous  publication1  and  will  not  be  dwelt  upon  here  further 


1  Stockberger,   W.   W.     The  Necessity  for  New   Standards  of  Hop  Valuation. 
33,  Bureau  of  Plant  Industry,  TJ.  S.  Dept.  of  Agriculture.     1909. 
271 


Circular 


PHYSICAL   AND  CUEMICA1     VALUATION    COMPARED 


17 


than  to  Btate  thai  it  is  well  nigh  impossible  to  find  two  pei  one  who 
will  assign  the  same  rani  in  value  to  -i\  samples  of  commercial  Imps 
selected  at  random.  Some  light  i-  thrown  on  these  differenct 
judgment  by  a  study  of  the  different  opinions  rendered  ss  t<>  the 
relative  value  «>f  the  four  h>t-  of  hops,  all  from  the  Bame  Bource  but 
subject  to  different  conditions  of  treatment  and  storage.  In  order 
ti>  bring  out  clearly  Borne  of  the  contrasts  in  these  opinions,  a  table 
was  prepared  in  which  the  physical  and  chemical  valuations  are 
compared.  In  this  table  the  relative  rank  given  each  l"t  of  Imps 
by  the  four  expert  judges  is  indicated  by  the  corresponding  numeral. 
The  relative  rank  in  acidity  of  1 1  u*  oils,  which  is  similarly  indi- 
cated; was  determined  from  the  results  of  the  first  analysis,  since  this 
analysis  was  made  nearest  in  point  of  time  to  the  physical  filia- 
tions. The  hops  having  the  oils  lowest  in  acidity  were  given  the 
highest  rank,  those  with  oils  next  in  acidity  second  rank,  and  SO  on, 
tin-   order  being  determined    by    the    fact    that    the   hops   having  oils 

lowest  in  acidity  had  changed  least  from  the  original  condition  at 
the  lime  of  first  storage.  The  relative  rank  with  respect  to  ester 
content  \\;i-  determined  in  the  same  manner.  The  relative  rank 
with  respect  to  resins  was  determined  from  the  content  of  soft 
.  as  these  alone  are  considered  to  he  the  only  resins  of  value  in 
the  utilization  of  hop-.  Since  keeping  quality,  as  indicated  by  a 
slow  rale  of  change  in  the  chemical  constituents,  is  an  important 
factor  of  value  it  was  made  the  basis  <»f  relative  rank  in  this  case 
rather  than  the  absolute  quantity  of  -oft  resin.  This  relative  keep- 
ing quality  was  determined  from  the  difference  in  the  content  of  soft 
resin.-,  a-  shown  by  the  two  analyses.  A  direct  compari.-on  of  all 
these  relative  rankings  may  Ik1  made  from  Table  V. 

Tabu  y.     Comparisons  of  rankings  in  t  tulphured  <m<i  tuuutphured  hops 

in  cold  storage  nmi  in  ordinary  *t<>rnge. 


Previous  trentment  of  the  hops. 


Rank  In  value  determined  as  noted. 


By  trade  experts. 


A. 


By 

acidity. 


By 

ester 
eon- 
tent. 


By 

I 
quality 
ot  .« ' i f t 

r s. 


Sulphured,  rold  stored- 

I'nsuiphured.  cold  stored 

Sulphured,  ordinary  stored 

Unsulphured,    ordinary  stored. 


From  this  table  it  appear?  that  the  rankings  as  to  value  are  con- 
sistent in  one  case  only,  that  of  the  sulphured  cold-stored  hops.  How- 
ever, on  taking  the  judgments  of  the  trade  experts  singly,  that  of 
expert    A   will    be  seen   to  agree   with  the  rankings  determined   by 


18  SOME   EFFECTS   OF   REFRIGERATION    OX    HOPS. 

acidity,  that  of  expert  C  with  the  rankings  with  respect  to  ester  con- 
tent, while  the  rankings  of  experts  B  and  D  agree  with  the  order 
determined  by  the  keeping  quality  of  the  soft  resins.  The  reason  for 
the  differences  in  the  judgments,  based  largely,  if  not  entirely,  upon 
the  flavor  or  aroma  of  the  hops,  seems  to  lie.  in  part  at  least,  in  the 
difference  of  degree  of  sensitiveness  of  the  individual  to  the  several 
volatile  constituents,  which  together  form  the  aroma.  It  is  well 
known  that  odors  which  are  agreeable  to  some  persons  affect  others 
unfavorably,  and  there  is  every  reason  to  believe  that  in  the  present 
case  the  differences  in  judgment  were  due  to  the  physiological  idiosyn- 
crasies of  the  observers.  That  this  point  of  view  is  coming  into 
wider  recognition  is  shown  by  the  following  statement  made  by 
Dr.  Albert  Fischer: 

The  determination  of  aroma  is  an  entirely  individual  matter,  depending  upon 
the  individual  taste,  the  state  of  health,  and  the  eventual  influence  of  outside 
flavors  on  the  person  testing.1 

However,  since  the  number  of  individuals  who  passed  judgment 
upon  the  experimental  samples  was  small,  the  decisions  rendered  are 
not  necessarily  conclusive  and  certainly  do  not  prove  that  the  aroma 
should  not  be  used  as  a  factor  in  the  determination  of  the  value  of 
hops.  That  the  aroma  is  useful  in  determining  the  age  and  sound- 
ness of  hops  is  conceded  even  by  those  who  hold  that  it  -is  not  a 
proper  factor  from  which  to  determine  intrinsic  value.  The  term 
"  age  "  may  be  used  to  express  the  time  that  has  elapsed  since  the 
hops  were  harvested  or.  in  a  relative  sense,  to  denote  the  extent  to 
which  unfavorable  changes  have  occurred  in  the  hops.  The  hops 
under  discussion  here  were  of  the  same  actual  age.  but  owing  to  the 
different  conditions  of  treatment  they  were  of  different  relative  ages, 
as  shown  by  the  different  points  to  which  the  changes  in  the  chemical 
constituents  had  progressed  at  the  time  of  analysis.  From  the  several 
classifications  shown  in  Table  V  it  is  evident  that  the  relative  age 
and  degree  of  deterioration  as  determined  from  analysis  will  depend 
very  largely  upon  which  one  of  the  various  constituents  is  selected 
as  the  basis  of  comparison.  Similarly,  the  estimation  of  age  or  dete- 
rioration from  the  impressions  produced  by  the  aroma  will  vary 
according  to  the  individual  peculiarities  of  taste  or  fancy  possessed 
by  the  observer.  It  is  much  to  be  regretted  that  there  is  not  a  better 
understanding  of  the  relations  between  the  factors  commonly  con- 
sidered in  establishing  the  relative  market  value  of  hops  and  the 
actual  value  of  the  hops  in  the  processes  in  which  they  are  utilized. 
The  determination  of  a  definite  basis  of  value  from  which  sound 
standards  could  be  derived  would  have  great  practical  importance, 
both  for  the  producers  and  for  the  consumers  of  hops. 

1  Fischer,  A.  Modern  methods  of  hop  analysis.  Letters  on  Brewing,  vol.  11,  1912, 
p.   317. 

271 


i.i  \  i  I  vi     BIONIFIOANOB  OS    PHH    BJ  81  i  is.  !'.» 

GENERAL    SIGNIFICANCE   OF   THE   RESULTS. 

The  material  which  furnished  the  basis  for  the  observations  dis 
cussed  in  tlii-  paper  was  prepared  primarily  with  the  view  to  < l<t ••!-- 
mining  the  feasibility  of  abandoning  the  practice  of  sulphuring  bops. 
Some  previous  experiments  had  shown1  thai  under  certain  conditions 
there  was  some  danger  of  bops  becoming  slightly  contaminated  with 
arsenic  *  1 1 1 1- i 1 1 ir  the  process  <>!'  sulphuring,  to  obviate  which  the  dis- 
continuance of  tin'  use  i>t"  sulphur  was  naturally  suggested.  It  was 
expected  that  the  unsulphured  hops  would  be  received  with  Less 
favor  by  the  trade  than  those  which  bad  been  sulphured,  owing  to 
the  more  pronounced  variations  in  the  color  of  the  former,  but  at 
the  time  tli«'  bales  of  hops  selected  for  observation  were  placed  in 
storage  the  difference  in  general  appearance  was  comparatively  small, 
although  the  sulphured  hops  could  be  readilj  distinguished  by  their 
more  uniform  and  somewhal  brighter  color.  A  study  of  the  trade 
opinion-  rendered  on  these  hops  after  they  had  been  for  some  tune 
in  storage  apparently  Bhows  thai  the  difference  in  appearance  due 
to  Bulphuring  becomes  accentuated  with  age  and  thai  the  preference 
is  for  the  sulphured  hop. 

When  freshly  cured,  the  difference  in  color  between  sulphured  and 
unsulphured  hop-  is.  as  a  rule,  much  more  pronounced;  and,  however 
careful  the  grower  might  be  to  harvesl  his  crop  at  the  stage  of 
maturity  besl  calculated  t<>  give  the  greatest  uniformity  in  color,  it  is 
evident  that  in  marketing  his  product  he  would  have  to  sees  for  those 
consumers  who  have  a  preference  for  the  greenish  grades  of  hops. 

Prom  the  results  of  the  chemical  tests  it  is  apparent  thai  unsul- 
phured hops  are  less  suited  to  the  requirements  of  the  consumer  than 
those  thai  have  been  sulphured,  especially  when  they  are  stored  for  a 
considerable  length  of  time  before  they  are  used.  However,  the  fact 
should  not  he  1 « > - 1  sighl  of  that  these  tests  were  made  on  hops  which 
had  been  in  storage  for  more  than  two  years,  and  the  changes  ob- 
served are  certainly  considerably  greater  than  those  which  occur  in 
hop-  which  have  been  stored  for  a  -hotter  period.  Nevertheless,  the 
greater  part  of  the  changes  in  certain  constituents  take-  place  during 
the  tir-t  year  of  storage,  a-  ha-  been  shown  by  Heron-'  in  the  case 
of  the  tannin  of  hop-.  Bui  from  the  work  of  Mo-eiv  who  found 
that  the  tannin  content  of  unsulphured  samples  was  consistently 
smaller  than  that  of  sulphured  samples  of  the  same  sorts,  it  is  evident 
that  the  oxidation  of  the  tannin  i-  retarded  by  sulphuring.     It  may 

1  Stnckbrr-'or.  W.  W.  The  Bonrci  -  "f  arsenic  in  certain  sampl.s  of  dripil  hup-;.  Bulle- 
tin 121,  pi.  4.  Bnrei I  Plant  Industry,  r.  s    Depl    "f  Agriculture      1908 

•  Heron,  John.  The  tannin  ..f  bops  Journal  of  tin-  Federated  Institutes  of  Brewing, 
rol    .'.   1896,  p    172 

■Cited  by  Braunpirt  in  Der  Bopfen,  Munich,  1901,  p.  B49. 

211 


20  SOME   EFFECTS   OF   REFRIGERATION   ON   HOPS. 

be  safely  assumed,  however,  that  sulphuring  is  an  effective  means  of 
retarding  chemical  changes  in  hops  from  the  time  they  are  cured  until 
they  have  reached  the  desirable  limit  of  age,  usually  determined  by 
commercial  conditions,  provided  such  hops  are  held  in  cold  storage. 

It  is  fully  realized  that  the  conclusions  drawn  in  this  paper  are 
subject  to  the  criticism  that  the  analyses  are  too  few  in  number  and 
that  they  are  not  coordinate  in  point  of  time  with  each  other  and 
with  the  physical  valuations.  Certain  obstacles  encountered  in  the 
course  of  the  work  made  it  impossible  to  round  out  the  results  as 
fully  as  was  desired,  yet  it  is  believed  that  the  coordinations  sug- 
gested by  the  facts  developed  are  of  sufficient  importance  to  justify 
this  somewhat  incomplete  presentation,  which  should  be  regarded 
more  as  a  report  of  progress  than  as  an  attempt  at  a  full  elucidation 
of  the  problem,  for  which  much  further  experimentation  is  necessary. 

SUMMARY. 

Material  for  a  comparative  study  of  the  effects  of  cold  and  ordinary 
storage  on  sulphured  and  unsulphured  hops  was  secured  from  a  hop 
field  in  the  Sacramento  Valley,  Cal.  The  green  hops  were  divided 
into  two  lots,  only  one  of  which  was  sulphured  during  the  process  of 
drying.  Bales  from  each  lot  were  placed  in  cold  and  in  ordinary 
storage,  and  samples  from  these  bales  were  drawn  from  time  to  time 
for  examination  with  respect  to  physical  condition  and  certain  chemi- 
cal constituents. 

At  intervals  of  7  and  18  months,  respectively,  from  the  time  the 
hops  were  placed  in  storage,  samples  were  drawn  and  submitted  to 
trade  experts,  who  were  asked  to  rate  the  samples  according  to  their 
relative  quality.  All  agreed  that  the  sulphured  hops  in  cold  storage 
were  best  in  quality,  but  opinion  was  divided  as  to  the  relative  merit 
of  the  three  other  lots. 

Determinations  were  made  of  the  acidity  and  ester  content  of  the 
volatile  oils  extracted  from  samples  of  the  hops  under  each  condi- 
tion of  storage.  The  conclusions  drawn  from  these  analyses  are  that 
both  sulphuring  and  cold  storage  retard  changes  in  the  hops  leading 
to  an  increase  in  acidity  and  ester  content  of  the  oils.  Cold  storage 
is  apparently  more  effective  than  sulphuring  in  retarding  the  increase 
in  acidity,  but  is  less  efficient  than  sulphuring  in  retarding  increase  in 
ester  content.  Cold  storage  and  sulphuring  combined  are  much  more 
effective  in  retarding  changes  in  acidity  and  ester  content  than  either 
alone. 

The  percentage  of  decrease  in  the  content  of  soft  resins  was  less 
in  the  cold-stored  hops  than  in  those  in  ordinary  storage.  The  evi- 
dence from  the  analyses  goes  to  show  that  the  sulphuring  tends  to 

271 


SI    M  M  1ST.  21 

retard  changes  in  the  content  <>f  Boft  rasinB  only  w  hen  combined  with 
cold  storage. 

Iiii'lr  experts  to  whom  Bamples  of  the  bops  under  considerat 
were  submitted  for  physical  judgmenl  differed  widely  in  their 
ions  of  relative  merit,  except  in  the  case  of  the  sulphured  cold  Btored 
hops,  which  all  agreed  ranked  first.    The  relative  rank  in  merit  as 
determined  From  each  of  the  Factors  Bought  in  analysis  was  Found 
to  give  corresponding  differences.    A  comparison  <>f  these  differences 
in  the  physical  and  chemical  valuations  shows  that  the  determination 
of  the  value  of  hops  From  the  aroma  depends  upon  the  pen 
taste  of  the  observer  and  is  greatlj  affected  by  the  in  lividual's  pref- 
erence or  dislike  of  one  or  the  other  of  the  several  constituents  oi"  the 
aroma. 

o 


UNIVERSITY  OF  FLORIDA 


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